What "No-Intro" does is fill some .dat files, to be used with ROM-Managers, with information about the known ROMS released. Often there are more versions of the same ROM dump, but most of them are garbage, some examples may include: bad dumps, hacks, fakes, overdumps, underdumps, and so on. "No-Intro" lists only the best available ROM; it must be a full dump with no faults and no changes to the file, basically just the ROMS that are the closest as possible to the original licensed cartridges.
This contains all of the publicly available ROMS in all of the No-Intro sets except for the "Nintendo - Nintendo 3DS", "Nintendo - Nintendo 3DS (DLC)", and "Nintendo - Nintendo DS" sets as of 2016-01-03.